Audible signal apparatus



Jan. 7, 1958 c. L. JACOBS v12,819,460

AUDIBLE SIGNAL APPARATUS Filed Dec. 24, 1954 ka "JP k, g

a E \J Q Q Q Car/fox? L z/acos v INVENTOR.

ATTORNEY United States Patent AUDIBLE SIGNAL APPARATUS Carlton L.Jacobs, Houston, Tex.

Application December 24, 1954, Serial No. 477,445

4 Claims. (Cl. 340-384) This invention relates to audible signalapparatus, and more particularly to electrical sound producingequipment.

While not limited to such use, the invention finds particularapplication in connection with audible alarm and warning equipment suchas fog horns and the like.

In the development of audible signal apparatus it has long been knownthat distance and direction are recognized by the harmonic content ofthe sound, the lower harmonics being first heard and the higherharmonics becoming recognizable as the source is approached. Thus, thefundamental is the first tone heard in approaching an audible signal andthe higher harmonics are heard in the increasing order of theirfrequencies. Audible .signal ap paratus, for use under conditions inwhich the indication of distance and direction of the sound source asthe same is approached is of importance, must therefore, be capable ofproducing a number of harmonics. This is especially true in the case offog horns, or the like, which must operate eifectively under greatlyVarying atmospheric conditions adversely affecting the transmission ofsound.

Heretofore various methods have been proposed for the production ofaudible signals making use of high and low harmonics, such as by the useof air actuated whistles, or electrical sound equipment in whichalternating current is separately generated at a number of differentfrequencies and the frequencies blended to provide mixed harmonics.Devices of this character have, however, not proved to be entirelysatisfactory, because of the relative complexity of the apparatusrequired or because of the large amount of power which must be expendedin the operation of the same. No satisfactory equipment of thischaracter has heretofore been available for the production of signalscontaining a number of harmonics by which direction and distance couldbe effectively recognized.

The present invention has for an important object the provision ofaudible signal apparatus which is capable of producing signals havingimproved characteristics whereby the distance and direction of the soundsource may be more easily recognized.

Another object of the invention is to provide audible signal apparatuswhereby signals of improved characteristics of recognizability as todirection and distance may be produced with a minimum expenditure ofpower and cost of equipment.

A further object of the invention is the provision of audible signalapparatus making use of an electrically driven loud speaker receivingcurrent from an alternating current generator, having means forfurnishing current to the field thereof which is of greater value duringone half of the cycle than during the other half thereof, wherebydistortion is produced in the output of the generator, which in turnproduces harmonics in the sound produced by the speaker, resulting in asound whose tonal quality makes it possible to easily recognize thedistance and direction of the sound source.

Another object of the invention is to provide audible signal apparatusof the kind referred to which is adjustable to permit the frequencies ofthe alternating cur- 2,819,460 Patented Jan. 7, 1958 ice rent producedby the generator to be altered, whereby the quality of the soundproduced by the speaker may be regulated to improve the distance anddirection recognition characteristics of the signals.

A further object of the invention is the provision of audible signalapparatus having means whereby the frequencies of the sound produced maybe adjusted as desired.

Another object of the invention is to provide audible signal apparatusof the type referred to which embodies improved electrically operatedtiming mechanism whereby the duration and frequency of the signals maybe adjusted as desired.

A still further object of the invention is to provide audible signalapparatus which is of simple design and economical to manufacture andwhich may be economically operated and maintained.

The above and other important objects and advantages of the inventionmay best be understood from the following detailed description,constituting a specification of the same, when considered in conjunctionwith the annexed drawings, wherein- Figure 1 is a circuit diagram,illustrating electrical circuits embodying the invention;

Figure 2 is a diagrammatic view showing the form of wave produced by thealternator of the invention and by which the sound producing means isoperated.

Referring now to the drawings in greater detail, the invention isillustrated in connection with its use in fog horn equipment includingone or more electrically operated horns such as that indicated at 10, ofconventional design, such as a loud speaker of the dynamic type, whichis connected to receive current from the stator 12 of an alternatingcurrent generator of usual construction having a field coil 14 which isrotatable relative to the stator. For the purpose of illustration, thestator may be constructed with three coils 13, and the horn 10 may beconnected by the conductors 16 and 18 across one of these coils. Meansis provided for controlling the supply of current to the horn, which maytake the form of a relay having an armature 20 and a coil 22, thearmature being arranged to open and close the circuit through theconductors 16 and 18. Conductor 18 is also connected to ground.

Suitable timing mechanism, described in detail hereinafter, is providedfor controlling the operation of the relay.

As ordinarily operated, the field coil 14 of the generator is suppliedwith direct current from a source such as the battery 38, in order toproduce alternating current whose instantaneous values are representedby a sine curve.

The operation of a horn of this type, however, from a source of currentwhose instantaneous values may be represented by a sine curve, does notprove satisfactory, because a sound wave of sine shape is not easilyrecognizable by the human ear, and does not give a sense of distance anddirection. In order to overcome this ditficulty, and to provide currentwhich will operate the horn in a manner to produce a sound havingimproved characteristics of distance and direction recognizability,means is provided for distorting the shape of the curve representing theinstantaneous values of the current from the generator. This may beaccomplished by altering the characteristics of the current supplied tothe field coil 14.

For this purpose a half-wave rectifier 30 is provided which is connectedto the stator 12 and to a resistor 32, which is also connected to aterminal 33 of a voltage regulator, indicated generally at 34,hereinafter described in greater detail. From the voltage regulatorcurrent is conducted through a conductor 108, connected to the terminal35, to a resistor 36 which is in turn connected to one side of thebattery 38. other side connected to ground.

The regulator 34 also has a terminal 39, which is connected to theterminal 35, through a conductor 41, into which a switch 52 is connectedwhereby this connection may be opened or closed. The voltage regulatoris contained in a casing 137 of conventional type, which may be of metalconstruction carrying the terminals 33, 35, 37 and 39 which areinsulated from the casing and the casing may also be connected to theground 135 and to conductors 116, 136 and 140 to ground the same.

By this arrangement the voltage across the field coil, during one halfcycle of the output across one of the coils of the stator, will be thevoltage of the battery plus the voltage drop across the resistor 36, andduring the other half cycle of the output of the same stator coil, willbe the voltage of the battery minus the voltage drop across the resistor36.

The instantaneous value of the current generated by the generatoroperated in this manner will be represented by a distorted curve and thecurrent so produced will contain a fundamental frequency and a number ofhar monies, and the horn, when operated by such current will producesound having improved characteristics which make it possible to easilyrecognize the distance and direction of the source.

The voltage regulator may be of usual construction, a preferred form ofwhich is illustrated in Figure 2. The regulator has an on-and-olt relayhaving a coil 114 and an armature 118, which moves into and out ofcontact with a stationary contact 120. A voltage regulating relay isalso provided, having a coil 134, which is connected to the armature 118through a resistor 130 and conductor 132, and which is also connected tothe ground as indicated at 135, through conductor 136, so that when thearmature 118 is in contact with the contact 120, current may flow fromthe battery 38 through resistor 36, conductor 108, terminal 35,conductor 122, armature 118, resistor 130, conductor 132, to coil 134and thence to ground through conductor 136, to actuate the voltagecontrol relay upon an increase in the voltage across the battery.

A stationary contact 126 is provided for the armature 129, which contactis connected to the armature 118 through conductor 128 and conductor124, and armature 129 is also connected to the field coil 14 throughconductor 106, terminal 37, and conductor 56, whereby the field coil 14is connected to the battery and the resistor 36. Thus, the voltage onthe field coil 14 will, under these conditions, be the battery voltageplus the voltage drop across the resistor 36, when the armature 129 isin contact with the contact 126.

Another stationary contact 138 is provided for the armature 129, whichcontact is connected to ground through conductor 140.

The terminal 33 is connected to the conductors 124 and 128 by aconductor 98, which is also connected to the armature 129 through aconductor 101, resistor 100 and conductor 104.

Current from the stator 12 may flow through conductor 54, rectifier 30,resistor 32, terminal 33, conductor 98, conductor 124, armature 118,conductor 122, terminal 35, conductor 108 and resistor 36 to battery 38,to charge the battery. In the event that the voltage from the generatorexceeds a predetermined limit, the current through the coil 134 of theregulating relay will increase sufliciently to move the armature 129 outof contact with the contact 126 and into contact with contact 138, thusshort circuiting the field coil 14 through conductor 56, terminal 37,conductor 106, armature 129 and conductor 140. The generator voltagewill thereupon diminish.

It will be seen that with this arrangement the output voltage from thegenerator to the horn may be regulated by adjusting the resistor 32.

The battery 38 has its with the generator shaft.

The current to the relay coil 22 may be controlled by any desired typeof timing mechanism such as the cam operated switch indicated at 1.50having the switch blades 152 and 154 each provided with contact pointsand arranged to be operated by the cam 156 which may be mounted on ashaft 158 for rotation by any suitable means, as by means of a drivingconnection not shown, Switch blade 152 is connected to the coil 22 andswitch blade 154 is connected to the conductor 41. Upon rotation of thecam 56 the switch will be closed by the projection 160 of the cam topermit current to flow to the coil 22 whereby the armature 20 will bemoved to close the circuit to the horn through conductors 16 and 18.

While the invention is disclosed herein in connection with certainspecific embodiments of the same, it will be understood that this isintended by Way of illustration only and that numerous changes can bemade in the character and arrangement of the various parts Withoutdeparting from the spirit of the invention and within the scope of theappended claims.

Having thus clearly shown and described the invention, what is claimedas new and desired to secure by Letters Patent is:

1. Audible signal apparatus comprising electrically operable soundproducing means of the magnetically operable vibrating diaphragm typeresponsive to an alternating electrical current to produce an audiblesignal, an alternating current generator having a stator Winding and afield coil, a first electrical circuit including said means and saidstator winding, a source of direct current, a second electrical circuitincluding said stator winding, said'source and said field coil forsupplying direct current to said field coil, and means in said secondcircuit for continuously varying the voltage of the current supplied tosaid field coil to cause variations in the wave form of the currentsupplied to said sound producing means.

2. Audible signal apparatus comprising electrically operable soundproducing means of the magnetically operated vibrating diaphragm typeresponsive to an alternating electrical current to produce an audiblesignal, an alternating current generator having a stator winding and afield coil, a first electrical circuit including said stator winding andsaid means for supplying alternating current to said means, a source ofdirect current, a second electrical circuit including said field coiland said source, and means forming an electrical connection between saidstator winding and said second circuit and responsive to the current insaid stator winding to continuously vary the voltage of the currentsupplied to said field coil to cause variations in the wave form of thecurrent supplied to said sound producing means.

3. Audible signal apparatus comprising electrically operable soundproducing means of the magnetically operated vibrating diaphragm typeresponsive to an alternating electrical current to produce an audiblesignal, an alternating current generator having a stator winding and afield coil, a first electrical circuit including said winding and saidmeans to supply alternating current to said means, a source of directcurrent, a second electrical circuit including said source and said coilfor supplying direct current to the coil, means forming an electricalconnection between said second circuit and said Winding and responsiveto the flow of current in one direction through said winding to cause aflow of direct current of continuously varying voltage from said Windingthrough said second circuit to cause a variation in the Wave form of thecurrent supplied to said sound producing means, and voltage regulatingmeans in said second circuit operable to limit the voltage applied tosaid sound producing means.

4. Audible signal apparatus comprising electrically operablesoundproducing means of the magnetically operated vibrating diaphragm typeresponsive to an alter nating current to produce an audible signal, analternating 5 current generator having a stator winding and a fieldcoil, a first electrical circuit including said winding and said meansfor supplying alternating current to said means, a source of directcurrent, a second electrical circuit including said source and said coilfor supplying direct current to the coil, means forming an electricalconnection between said winding and said second circuit and responsiveto the flow of current in one direction through said Winding to cause acontinuous variation in the voltage of the current in said secondcircuit during one-half cycle 10 of the alternating current from saidgenerator to cause a variation in the wave form of the current suppliedto said sound producing means.

References Cited in the file of this patent UNITED STATES PATENTSYtterberg Mar. 7, 1939 Curl Dec. 7, 1948 Crane Mar. 7, 1950 Fleming Nov.27, 1951 FOREIGN PATENTS Great Britain Aug. 18, 1932

